Interpretive Summary: Beit Alpha is a cucumber type widely cultivated in Mediterranean regions for fresh market consumption. Although its cultivation in other production areas is relatively recent, knowledge about its historical roots is sparse. It is thought to have originated in Israel where it is well suited to extreme environmental conditions, especially high temperatures (97 to 120 degrees F). Despite its popularity, there have been no efforts by public breeding programs to improve this market type. Traditionally, the Beit Alpha market type has been grown under protected "hoop house" conditions, which allows for environmental control such that continuous cropping can occur in some growing environments. Depending on the cropping season, fruits from single plants can be harvested up to 30 times and yield as many as 65 moderately small (7 to 9 inches in length), slightly curved, smooth-skinned, dark green fruit. Such prolific fruit production is due to the presence of multiple pistillate flowers per node and a relatively high number of primary lateral branches. These and culinary characteristics are critical considerations when developing best management practices for this crop. Although this market type is not currently grown in the U.S., there is increasing interest among U.S. fresh market growers to include this type in their market portfolio. Therefore, a study was designed to increase develop genetic populations (i.e., inbred lines) of this market type by complex matings with another commercial cucumber type followed by improvement using biotechnologies (i.e., marker-assisted selection = MAS). The resulting progeny were evaluated in field trials to determine their potential for use in modern plant breeding programs. The results indicated that the resulting progeny were very diverse genetically (as defined by MAS) and had yield and quality characteristics that would allow their successful inclusion into private and public plant breeding programs for cucumber improvement. The resulting progeny will provide a new source of plant material currently not available in commercial cucumber to improve the yield and quality of this crop species. The resulting products (cultivars) will make the U.S. grower more competitive in the global market place and provide managerial flexibility that does not now exist in production of this crop.

Technical Abstract:
Beit Alpha cucumber (Cucumis sativus L.) is a Mediterranean fresh-market type with a relatively narrow genetic base. To broaden its base for plant improvement, 42 diverse accessions were compared employing a previously defined standard marker array to choose wide-based parental lines for use in backcross introgression. Inbred backcross lines (IBL) were developed by crossing Beit Alpha line '04HD5' (De Ruiter Seeds, The Netherlands; recurrent parent) and PI 285606 (Poland; donor parent), and then selecting the most genetically diverse BC1 and BC2 progeny based on molecular marker profiles, followed by three generations of single-seed descent to produce 117 IBL. Molecular genotyping of IBL was then performed, and IBL were evaluated for days to anthesis, sex expression, pistillate flowers per node, lateral branch number, fruits per plant, fruit length, and fruit weight in the U.S., The Netherlands, Israel, and Turkey. Multivariate analyses and genetic distance comparisons indicate that IBL possessed considerable inter-line morphological and genotypic diversity. These diverse IBL will be useful in genetic studies and to evaluate Beit Alpha cross-progeny derived from IBL x elite germplasm created to broadened genetic base of this market type.